Silicon Nitride Bonded Silicon Carbide Bricks Description
Si3N4 bonded SiC bricks is composite refractory material in which Si3N4 is principal bonding phase, the main crystalline phase of silicon nitride bonded silicon carbide brick is SiC, secondary crystalline phase is α-Si3N4, and β-Si3N4. In most Si3N4 bonded SiC products, α-Si3N4 is the primary bonding phase. Usually, Si3N4 bonded SiC refractory bricks raw materials are high purity SiC and Si powder, green body is made by vacuum grouting method or pressure slurry injecting method. Green Si3N4 bonded SiC bricks are sintered in nitrogen atmosphere, so Si and N2 will have nitridation reaction and form Si3N4.
Si3N4 Bonded SiC Bricks Advantages
Silicon nitride bonded SiC bricks have excellent high temperature mechanical performance, excellent creep resistance, 0.2Mpa refractoriness under load beginning point is higher than 1800℃
High modulus of rupture at high temperature, high thermal conductivity, excellent molten alkaline material and alkaline vapor corrosion resistance. good high temperature oxidization resistance, as at high temperature oxidization atmosphere, silicon nitride bonded silicon carbide bricks surface will form dense SiO2 protection layer, which can keep the future oxidization.
Si3N4 bonded SiC bricks have excellent thermal shock resistance, thermal shock resistance ability is usually larger than 25 times.
Silicon nitride bonded SiC bricks have excellent CO corrosion resistance and metal oxides slag corrosion resistance.
Si3N4 bonded SiC products have excellent cryolite corrosion resistance. The lower the apparent porosity, the better the cryolite corrosion resistance.
Si3N4 Bonded SiC Bricks Physiochemical Index
| Item |
Si3N4 bonded SiC brick |
Sialon bonded SiC brick |
Fine Si3N4 bonded SiC brick |
| SiC % |
75.04 |
73.54 |
66~80 |
| Si3N4 % |
22.18 |
/ |
20~30 |
| Al2O3 % |
0.37 |
/ |
/ |
| Fe2O3 % |
0.27 |
0.32 |
/ |
| Bulk density g/cm3 |
2.73 |
2.72 |
2.80 |
| Apparent porosity % |
13.3 |
14 |
≤11 |
| Cold crushing strength Mpa |
229 |
220 |
580 |
| Modulus of rupture Mpa（1400℃） |
65.2 |
56.7 |
180 (1200℃) |
| Linear expansion coefficient ℃-1 (20~1000℃) |
4.5*10-6 |
4.7*10-6 |
4.4*10-6 |
| Thermal conductivity w·（m·K）-1 1000℃ |
18.4 |
18.2 |
/ |
Si3N4 Bonded SiC Bricks Application
Si3N4 bonded SiC brick is ideal refractory product for blast furnace inner lining. Blast furnace refractory lining corrosion mechanism includes: alkali corrosion(40%), oxidization(CO, Zn, SiO and H2O vapor), abrasion(10%), bad thermal conductivity(10%), thermal shock(15%) and slag corrosion(5%). Si3N4 bonded SiC bricks have excellent corrosion resistance to the up mentioned factors. Silicon nitride bonded silicon carbide bricks lined blast furnace lining has 10~15 years of service life. Newly built large capacity blast furnace middle part inner lining or cooling wall bricks all adopt Si3N4 bonded SiC bricks.
SiN4 bonded SiC refractory is the best choice of new generation aluminum reduction cell inner lining. It has the advantages of decreasing horizontal electric current, increasing side part heat diffusion, reducing cell temperature, improving electric current efficiency and energy saving. Aluminum reduction cell life is significantly prolonged. Because SiN4 bonded SiC bricks have good thermal conductivity, excellent cryolite corrosion resistance, oxidization resistance and scouring resistance, it can form stable protection layer at working surface.
